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| class Solution {
public:
int calculate(string s) {
stack<int> stk;
int cur = 0, sign = 1, ans = 0;
for (char c : s) {
if (c == ' ') continue;
else if (c == '+') {
ans += sign * cur;
cur = 0;
sign = 1;
} else if (c == '-') {
ans += sign * cur;
cur = 0;
sign = -1;
} else if (c == '(') {
stk.push(ans);
stk.push(sign);
ans = 0;
sign = 1;
} else if (c == ')') {
ans += sign * cur;
cur = 0;
ans *= stk.top(); stk.pop();
ans += stk.top(); stk.pop();
} else {
cur = cur * 10 + (c - '0');
}
}
if (cur != 0) ans += sign * cur;
return ans;
}
};
|